我不是她爱的那个姑娘
[wŏ bù shì tā ài de nèi gè gū niáng]
Translates to 'I am not the girl she loves'. Conveys a sense of being left out in love, often used by a third party in love triangle scenarios where the speaker acknowledges they cannot match up to someone who receives the affection of the person they care for.